Telephone customers have recently been offered the service option of making their own installation changes and desk sets having cords which may be plugged in at various points on the customer premises having suitable jacks provided therefor are well known. This obviously represents considerable savings to a customer since the expense of an installer visit is obviated. Wall-mounted telephones which may be readily installed or removed from wall plate receptacles are also now familiar and have offered particular convenience to customers demanding more choice in the telephone location. In such arrangements, wall plate receptacles are permanently mounted at desired points on the customer premises, which receptacles provide outlet jacks for the permanent telephone wiring. A pair of vertically aligned, flanged mounting studs are provided on the face of the wall plate. The telephone set is then simply mounted by fitting a pair of corresponding slotted apertures in the telephone set backplate over the studs and sliding the slots downward behind the stud flanges. Wiring connections are simultaneously made by a plug extending from the telephone backplate, which plug is adapted for adjustable insertion in the wall plate jack. In one prior art arrangement disclosed in the patent of R. C. Ward et al., U.S. Pat. No. 3,898,394 issued Aug. 5, 1975, an adapter assembly is provided to which a wall-mounted telephone set, previously permanently affixed, may be permanently attached. The adapter may then be removably mounted on the wall plate as described in the foregoing. This arrangement initially requires tools and skills of the same level required of the installer who made the original permanent wall installation.
In some cases, a customer may request more flexibility than that offered even by a virtually portable telephone of the character described in the foregoing. Thus, for example, with a removable wall telephone set mounted in one room, a customer may require a self-installable extension telephone at a distance from the first telephone in the same room or in an adjoining room. One prior art extension cord for multiple plug-in telephones is disclosed in the patent of B. W. Gumb et al., U.S. Pat. No. 4,047,787 issued Sept. 13, 1977. The cord arrangement there described provides for a single plug at one end of the cord and a junction box at the other having a pair of paralleled jack outlets. A cord arrangement of this character is manifestly not compatible with a wall-mounted telephone set where the single wall jack is already occupied by the telephone set plug. It is thus one objective of the present invention to provide a customer installable wall-mounted telephone adapter assembly which permits the connection of an extension telephone for location at a distance from the first telephone. In the design of any such customer installable equipment, a number of factors must be taken into consideration. The level of skill and the availability of the proper tools, for example, may be limited for many customers. With respect to an adapter assembly specifically, it may not be immediately recognized that the adapter and the wall-mounted telephone are separate units. Thus, some means must be provided to ensure that both are not removed from the wall when only the telephone set is to be moved. It is to these and other problems to which the adapter assembly of the invention is chiefly directed.